THE PRECAMBRIAN ROCKS OF THE CANTON QUADRANGLE 45 



been driven into the hill at different levels, following the strike 

 of the ore-bearing gneiss, which is here about lo or 12 feet thick. 

 Thence southeastward and southward the formation follows the left 

 brink of the gorge, outcropping interruptedly, with the prospector's 

 assistance, and dipping steeply away from the river. At the lower 

 end of the paper mill (shown on the map by the "inverted L "- 

 shaped building) the stratum passes over to the right bank, which 

 it follows rather closely, till near its southern extremity it crosses 

 the river again and pinches out somewhere on the small island just 

 below the upper dam. The gneiss, and where it is observable, the 

 foliation of the gabbro, pitch in general westward. The variation 

 of strike noted at the lower end of the gorge is doubtless to be ac- 

 counted for by an open pitching anticline whose axis, as is the case 

 in the majority of demonstrable folds southeast of the Harrison 

 Creek limestone belt, is directed toward the west or west-northwest, 

 and at an angle of probably 45 degrees or more. 



No special alteration of the xenolith by the gabbro was observed 

 at any of the contacts exposed. At the south end of the ore body 

 and along the upper half of the gorge, the inclosing rock is a highly 

 sheared hornblende gneiss, not varying essentially from the normal 

 amphibolite of the surrounding area. The upper contacts at the 

 middle and north end of the formation are likewise of the same 

 character. The rock underlying the pyritic layer in the immediate 

 vicinity of the mill is, however, somewhat abnormal in that it is 

 spotted with numerous clusters of small biotite flakes which give 

 the ledge a spangled appearance, but this is not to be regarded as in 

 any sense a contact phase. That underlying the pyrite layer at the 

 big gossan is a coarse-grained amphibolite almost wholly altered to 

 chlorite and serpentine for a distance of 40 or 50 feet from the con- 

 tact. Though this association is very suggestive of an endomorphic 

 alteration in the vicinity of the inclusion, it is in all probability due 

 to an accidental localization of hydatogenic activity at this point, as 

 the same sort of alteration has sometimes been observed Avhere 

 there is no Grenville xenolith present to suggest itself as the 

 immediate cause. 



The pyritous layer itself is of essentially uniform constitution 

 from one end to the other and can not be said to exhibit any mar- 

 ginal alterations attributable to the special influence of the basic 

 magma. If such influence has been exerted on this inclusion it 

 must have affected the stratum as a whole, and in this case either 

 the general metamorphism of the gneiss is due solely to its entomb- 

 ment in the gabbro, or else the effects of the latter, in whatever de- 

 gree they may have been operative, were added uniformly to those 



